Recent evidence suggests that the nuclear membrane, or perhaps more directly, the proteinaceous nuclear matrix is the reactive surface or spatial organizer for wide range of nuclear events, e.g. - replication, hormone-growth factor stimulation, nuclear-cytoplsmic transport, viral assembly, carcinogenesis, chromatin assembly, RNA transport along ribonucleoprotein networks, and nuclear pore assembly. It is the purpose of ths proposal to use a number of biophysical approaches to delineate biodynamic properties of the nuclear membrane and matrix. Lateral diffusion of membrane components as measured by fluorescence recovery after photobleaching (FRAP) methodology will serve as a probe of membrane state and structure. In addition, fluorescence spectroscopy and fluorescence energy transfer will be employed in conjunction with fluorescently tagged membrane and matrix components to ascertain specific alterations in spatial arrangement of matrix polypeptides due to known nuclear ligands, e.g. - insulin, EGF, Ca++-Mg++, viral antigens, carcinogens. Affinity constants of these ligands for nuclear matrix will be obtained by fluorescence titration measurements. These experiments will initially be performed on nuclei isolated from rat liver and will require fluorescent and other chemically modified derivatives of purified matrix and membrane proteins. These modified proteins will also be employed in readdition experiments to whole nuclei and reconstitution studies. A necessary adjunct to these dynamic investigations will be a more detailed biochemical characterization of nuclear membrane and new methods for selective extraction of nuclear membrane and matrix proteins.